From: Theodore Ts'o Subject: Re: [PATCH] CPU Jitter RNG: inclusion into kernel crypto API and /dev/random Date: Tue, 29 Oct 2013 09:24:48 -0400 Message-ID: <20131029132448.GB691@thunk.org> References: <2579337.FPgJGgHYdz@tauon> <2049321.gMV6JUDze7@tauon> <20131028214549.GA31746@thunk.org> <3160817.9DcncHidey@tauon> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: sandy harris , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org To: Stephan Mueller Return-path: Received: from imap.thunk.org ([74.207.234.97]:52040 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753241Ab3J2NYx (ORCPT ); Tue, 29 Oct 2013 09:24:53 -0400 Content-Disposition: inline In-Reply-To: <3160817.9DcncHidey@tauon> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Tue, Oct 29, 2013 at 09:42:30AM +0100, Stephan Mueller wrote: > Based on this suggestion, I now added the tests in Appendix F.46.8 where > I disable the caches and the tests in Appendix F.46.9 where I disable > the caches and interrupts. What you've added in F.46 is a good start, but as a suggestiom, instead of disabling one thing at a time, try disabling *everything* and then see what you get, and then enabling one thing at a time. The best thing is if you can get to the point where the amount of entropy is close to zero. Then as you add things back, there's a much better sense of where the unpredictability might be coming from, and whether the unpredictability is coming from something which is fundamentally arising from something which is chaotic or quantum effect, or just because we don't have a good way of modelling the behavior of the L1/L2 cache (for example) and that is spoofing your entropy estimator. Regards, - Ted